Conventionally, a Controller Area Network (CAN) used in an on-board system is known as one of Local Area Network (LAN) communication standards. Usually, at a dealership utility, a malfunction diagnosis (diagnosis) for diagnosing an ECU included in an on-board system is performed by connecting a service tool to CAN of the vehicle using a data link connector.
As well known, an ECU is able to wirelessly communicate with an external device. For example, an ECU that is communicable with a mobile device receives a remote operation via the mobile device, and functions as a remote operation device (refer to patent literature 1).
Further, an ECU, such as a Data Communication Module (DCM), is able to access to a wireless communication network and perform a wireless communication with a center positioned outside of the vehicle. The ECU performs a malfunction diagnosis to each of multiple ECUs that configure the on-board system using CAN of the vehicle.
Further, a technology in which the malfunction diagnosis to the ECU is carried out by both the service tool and the DCM is well known. In this case, while one of the service tool or the DCM performs the diagnosis malfunction to an ECU, the other one of the service tool or the DCM may request the malfunction diagnosis to the same ECU. In this case, as an arbitration method, the malfunction diagnosis started at a previous time may be carried out with a higher priority. After the malfunction diagnosis started at the previous time is ended, the malfunction diagnosis requested at a later time can be started under a specific rule (first come first processed).
However, in CAN, a maximum data size that can be transmitted in single frame is 8 bytes. Thus, when a data having a size larger than 8 bytes needs to be transmitted using CAN, the data is divided into multiple data segments and the multiple data segments are transmitted in predetermined order as multiple frames. The multiple frames configure one message. Thus, the data having a size larger than 8 bytes needs a relatively long time to be transmitted.
For example, suppose that a person visits a dealership utility by driving a vehicle and applies for a malfunction diagnosis service for diagnosing ECUs of the vehicle using the DCM. In this case, a message having a large data size is transmitted between the ECU and the DCM. Thus, until an end of the message transmitting, the malfunction diagnosis to the same ECU cannot be started using the service tool. Thus, the person who applied for the diagnosis service has to wait until the end of the message transmitting.
As described above, the first come first processed may cause some inconvenience to the customers of the diagnosis service. Thus, in some cases, the diagnosis needs to be carried out in a different rule other than the first come first processed rule. However, when each of the ECUs equipped to the vehicle is required to perform the switchover of the diagnosis processing rule, the process carried out in each ECU becomes complicated. Nowadays, a vehicle has great number of ECUs. Thus, a substantially great development cost may be required for adding the switchover function of the diagnosis processing rule to each ECU equipped to the vehicle.